The manufacture of reinforcement materials for rubber products, especially for tire cords, has been the subject of a great volume of research and innovation. This effort has focused on a number of facets, among which are concerns to produce better performing products while meeting the constantly demanding economic cost objectives of the global industry.
Alternative constructions have been proposed and patented for reinforcement materials in rubber articles and in particular rubber tires, such as modified cross-section monofilaments (DuPont Hyten®) or zero twist multifilament ribbons (Yokohama). However, the use of tire cords made from high tenacity organic fibers, such as rayon, nylon, aramid and polyester in a construction of moderate twist has remained the principal reinforcing method. High tenacity organic fibers impart improved fatigue properties and, when coated with an adhesion promoting agent, achieve excellent bonding to the surrounding rubber in the curing process for the manufactured article.
Traditional individual process steps for the production of a polyester- or nylon-based tire cord include the typical handling of materials from process machine to process machine within a facility and typical shipment from facility to facility between fiber producer, textile converter, treating unit, and tire builder. Obviously, these conventional processes involve a number of individual steps and multiple transfers of product and are both labor and cost intensive. In many instances involving traditional production processes, the cost of the treated cord is more than double the basic cost of producing the high tenacity fiber itself. Moreover, these conventional processes employ ply and cable twist machines, which at one time were prevalent as the standard.
Industry developments in the recent past have yielded changes to these traditionally treated tire cord production processes. For instance, the conversion industry in many cases is replacing old ply and twisting equipment with direct cable machines. These machines combine the ply and twisting step into one operation, thus rendering the tire cord production process more efficient and cost effective. Further, these machines produce larger package sizes and improve quality by requiring fewer knots or splices in the final cord product.
The methods used to build tires also have undergone significant developments. In many cases, current methods employ single-end treated cords rather than cut plies of a woven coated fabric as tire carcass reinforcement feed materials to the tire building machines. While the latter significantly reduces the space required and the cost incurred to build tires, the economics of traditional single-end treating processes are expensive.
The current invention addresses further major advancements in these manufacturing processes. Using recent developments in fiber production technology and adhesion chemistry, the key steps of converting a high tenacity fiber to a cabled, treated cord, having the physical and chemical properties needed to reinforce rubber products, can be carried out in a one-machine process. This eliminates the multiple package handling and multi-million dollar capital requirements for separate cord and fabric treating units. By the correct selection of each individual element, using the best individual technology, a satisfactory cabled treated cord may be produced very economically on a single machine, termed a one-machine cabled and treated cord unit (“OCT”).
The high tenacity organic fiber used in an OCT unit is selected and produced with physical properties such that when cabled and given a short term heat curing, the properties of the cord are satisfactory for the targeted end use. Individual feed yarns may be pretreated with adhesion promoters in their respective production processes or the individual feed yarn may be coated with adhesion promoters on the OCT unit. Individual feed yarns are cabled in a direct cable sub-unit, but the raw cabled cord so made is fed forward directly to a treating sub-unit without any prior package take up. The raw cabled cord is coated with an adhesion promoting dip. The coated raw cord is pulled through a heating unit under controlled tension, operated to achieve a desired temperature for a particular residence time to cure the adhesion dip prior to winding the treated cord on a package. Once packaged, the treated cable cord is delivered to product storage, preferentially by an automated conveyor pack out unit, prior to transfer out to customers or for further processing or manufacture.